The invention relates to an electric reflector lamp comprising:
a lamp vessel having an axis of symmetry and a neck-shaped lamp vessel portion which supports a lamp cap at a free end thereof, said lamp vessel having a first parabolically curved, reflectorized wall portion which merges into the neck-shaped wall portion and which has a first focus substantially on the axis of symmetry, and a second parabolically curved, reflectorized wall portion which has a second focus substantially on the axis of symmetry, and said lamp vessel being closed off with a light-transmitting window opposite the neck-shaped wall portion; PA1 a substantially linear electric light source with a geometric center, axially arranged in the lamp vessel in the first and the second focus; PA1 current conductors connecting the light source to the lamp cap. PA1 the second reflectorized wall portion is a body of revolution of a branch of a parabola having a second axis which encloses an acute angle .alpha. with the axis of the lamp vessel, and PA1 the first and the second focus are separate from one another.
Such a reflector lamp is known from EP 0 195 317. In the known lamp, the first and the second focus coincide, and the geometric center of the light source lies in said focuses. Radiation incident on the first reflectorized wall portion is so reflected for a major portion that it cannot issue to the outside until after it has been reflected once more. Light is lost, however, upon each reflection because no reflector material will reflect 100% of the incident light. Multiple reflections are accordingly disadvantageous for the useful output of a lamp. Another disadvantage of the known lamp is that the lamp provides a comparatively narrow beam when the light source is positioned axially.
A wider beam is indeed obtained when the described possibility of positioning the light source transversely is used in the known lamp, but this beam has the disadvantage that it is not rotationally symmetrical. An axial, linear light source is particularly suitable for that purpose. It is possible to obtain a wide beam with an axial light source, but then the lamp vessel must necessarily be comparatively wide, as is the case in lamps made of moulded glass such as PAR38 lamps. The lamp vessel there has a greatest width of 11 to 12 cm. This width differs strongly from that of reflector lamps having a blown lamp vessel and from the width of luminaires designed for them, which usually is 60 to 95 mm.
GB 2 166 861 A discloses an electric reflector lamp wherein a reflectorized paraboloidally curved portion merges into the neck-shaped lamp vessel portion, and merges via a reflectorized spherical portion into a second reflectorized paraboloidally curved portion. The focuses and the center of curvature of the reflectorized portions coincide. An incandescent body is positioned transversely in the focal plane. The spherical portion provides double reflections. The transverse incandescent body renders the beam non-rotationally-symmetrical.